Why are low-lying coastal areas especially vulnerable to tsunami damage?

Low-lying coastal areas are particularly vulnerable to tsunami damage because of how these waves transform as they approach land. In the deep ocean, tsunamis have enormous wavelengths but very small amplitudes, making them nearly imperceptible.12

However, as they reach shallower coastal waters, friction with the rising seafloor slows the waves, causing their wavelengths to shorten and their amplitudes to increase dramatically. This process, often described as fast-moving water stacking itself onto slower-moving water near the shore, can cause sea levels to rise as high as 30 meters (about 100 feet) in just 10 to 15 minutes.132

These powerful "run-ups" of rushing water can easily inundate low-lying terrain, uprooting trees, destroying buildings, and washing away entire coastal formations. The danger is compounded by the fact that the subsequent outflow of water can be just as destructive as the initial surge, and these oscillations may persist for several days.12